Multifunctional coated powders and high solids dispersions

ABSTRACT

A coated powder comprises (a) nanoparticles, and (b) a coating, on the surface of the nanoparticles. The coating comprises (1) silica moieties, (2) organo oxysilane moieties selected from the group consisting of mono-organo oxysilane moieties, bi-organo oxysilane moieties and tri-organo oxysilane moieties, and (3) poly(dialkyl)siloxane moieties.

BACKGROUND

Particles are added to enhance and modify the properties of manydifferent types of compositions and products. Examples includeultra-violet (UV) light absorbing particles, pigments, colorants,fillers, matting agents, optical diffusing particles, abrasion resistantparticles, viscosity modifiers, magnetic particles and reflectiveparticles. Especially in the case of nanoparticles, a very small weightpercent (wt %) of particles added to the composition or product candramatically affect properties. In order to be effective at such lowweight percents, the particles must remain dispersed and chemicallystable, during both the production and use of the composition orproduct. These problems are exacerbated as the dimensions of theparticles are reduced because of the increase in total surface area, ona weight basis.

Chemical instability can result from reaction of the particles withother reagents, as well as with agents present in the environment,during any of the phases of the composition or product, such asmanufacture, storage and use. Chemical instability may be exacerbated byenvironmental factors, such as exposure to visible and UV light, orexposure to elevated temperatures. Particle aggregation or poordispersability is often the result of incompatibility of the particlesurface with fluid components, especially incompatiblehydrophobic/hydrophilic and electrostatic interactions with solvents orother particulate additives. Particle aggregation or poor dispersabilitymay also be exacerbated by environmental factors, such as exposure toelevated temperatures, or long storage times. For large scale transportand ease of handling, it is often desirable to prepare liquiddispersions with high weight loading of the nanoparticles.

Particles comprising oxides are particularly suitable as additives,especially particles containing zinc oxides, titanium oxides, siliconoxides, aluminum oxides, iron oxides and/or rare-earth metal oxides.These oxides are thermodynamically stable, are typically unable to reactwith environmentally ubiquitous oxygen, and tend to be less reactivewith water than many other oxides and non-oxide materials. These oxidematerials have been used as pigments and abrasives for centuries.Nanoparticles consisting of certain metal oxides, most notably titaniumoxides, are particularly interesting for use in coating compositions,because they are usually colorless and transparent to visible light, andprovide protection against exposure to UV light; however they tend tohave poor photostability, caused by the photocatalytic behavior of theseoxides. In cosmetic preparations, poor photostability often manifests asa color change and is not acceptable for commercial topical skinproducts. Poor photostability also interferes with use in paints orother product coatings, resulting in reactivity and “chalking out”.

In order to improve dispersability in non-aqueous fluids, particles havebeen coated or surface treated with hydrophobic reagents. Coatings andsurface treatments have also been used to enhance chemical stability,including the photostability of titanium and other oxides.

T-Cote 031 is a microfine titania (titanium oxide) with a mean particlesize of less than 200 nm which has been treated with dimethicone(poly(dimethylsiloxane)) on the particle surface. The hydrophobicdimethicone surface treatment provides compatibility with non-aqueousoils that serve as liquid carriers in a variety of products. While thisnanoparticle material is used to produce dispersions at high weightloading, a major deficiency in photostability prevents its use indispersions intended for commercial use. The performance of T-Cote 031indicates that a simple dimethicone treatment is not sufficient toenhance photostability, as the photostability of this material is nearlyindistinguishable from uncoated microfine titania.

Aeroxide T805 is a fumed titanium dioxide powder which has been treatedto form octyl silane (H(CH₂)₈Si(O)₃) moieties on the particle surface.Presumably, the octyl silane coating is applied by reacting the particlesurface with a trifunctional alkoxy octylsilane such as triethoxyoctylsilane. While this treatment does not render the titania surfacecompletely inert, it is sufficiently chemically stable for somecommercial applications. Aeroxide T805 is sufficiently photostabile foruse as an additive in a cosmetic preparation, and is currently used inseveral topical human sunscreens. High solids dispersions are highlydesirable in sunscreen formulations since they enable high SPF (SunProtection Factor) values to be achieved while introducing a minimalamount of carrier fluid. However, difficulty is encountered when highsolids dispersions are formulated; typically a paste is formed. Thesehigh solids dispersions are commercially available, but due to highviscosity, they are difficult to mix with other reagents and are proneto waste since it is difficult to remove all of the material from thestorage container.

SUMMARY

In a first aspect, the present invention is a coated powder comprising(a) nanoparticles, and (b) a coating, on the surface of thenanoparticles. The coating comprises (1) silica moieties, (2) organooxysilane moieties selected from the group consisting of mono-organooxysilane moieties, bi-organo oxysilane moieties and tri-organooxysilane moieties, and (3) poly(dialkyl)siloxane moieties.

In a second aspect, the present invention is a process for producing acoated powder, comprising coating nanoparticles with a polymer. Thecoating is prepared by polymerizing a composition comprising (i) thenanoparticles, (ii) a first alkoxy silane selected from the groupconsisting of a tetra-alkoxy silane, a poly(tetra-alkoxy silane), andmixtures thereof, (iii) an organo alkoxysilane selected from the groupconsisting of mono-organo alkoxysilane, bi-organo alkoxysilane,tri-organo alkoxysilane, and mixtures thereof, and (iv) a second alkoxysilane selected from the group consisting of a poly(dialkyl)siloxane,and mixtures thereof.

In a third aspect, the present invention is a dispersion, comprising thecoated powders and a liquid carrier.

In a fourth aspect, the present invention is a composition comprisingthe coated powders and a resin.

In a fifth aspect, the present invention is a composition comprising thecoated powders. The composition is a paint, stain, coating, or ink.

In a sixth aspect, the present invention is a method of protecting skinfrom light, comprising coating skin with a composition comprising thecoated powders.

DEFINITIONS

The term “nanoparticle” means a particle having a particle size of atmost 999 nm. Preferably, a nanoparticle has a particle size of 10 nm to500 nm.

The term “particle size” means the average diameter of the image of theparticle as viewed by electron microscopy, unless otherwise stated. Theterm “average particle size” means the average of the particle sizes ofa collection of particles.

“High solids content” or “high weight loading” means that thecomposition referred to has at least 50 wt. % solid particle.

“Alkyl” (or alkyl- or alk-) refers to a substituted or unsubstituted,straight, branched or cyclic hydrocarbon chain, preferably containing offrom 1 to 20 carbon atoms. More preferred alkyl groups are lower alkylgroups, for example, alkyl groups containing from 1 to 10 carbon atoms.Preferred cycloalkyls have 3 to 10, preferably 3-6, carbon atoms intheir ring structure. Suitable examples of unsubstituted alkyl groupsinclude methyl, ethyl, propyl, isopropyl, cyclopropyl, butyl, iso-butyl,tert-butyl, sec-butyl, cyclobutyl, pentyl, cyclopentyl, hexyl, andcyclohexyl.

“Alkenyl” refers to a substituted or unsubstituted, straight, branchedor cyclic, unsaturated hydrocarbon chain that contains at least onedouble bond, and preferably having 2 to 20, more preferably 2 to 6,carbon atoms. Exemplary unsubstituted alkenyl groups include ethenyl (orvinyl) (—CH═CH₂), 1-propenyl, 2-propenyl (or allyl) (—CH₂—CH═CH₂),1,3-butadienyl (—CH═CHCH═CH₂), 1-butenyl (—CH═CHCH₂CH₃), hexenyl,pentenyl, and 1,3,5-hexatrienyl. Preferred cycloalkenyl groups contain 5to 8 carbon atoms and at least one double bond. Examples of cycloalkenylgroups include cyclohexadienyl, cyclohexenyl, cyclopentenyl,cycloheptenyl, cyclooctenyl, cyclohexadienyl, cycloheptadienyl, andcyclooctatrienyl.

“Alkynyl” refers to a substituted or unsubstituted, straight, branchedor cyclic unsaturated hydrocarbon chain containing at least one triplebond, and preferably having 2 to 20, more preferably 2 to 6, carbonatoms.

“Aryl” refers to any aromatic carbocyclic or heteroaromatic group,preferably having 3 to 10 carbon atoms. The aryl group can be cyclic(such as phenyl (or Ph)) or polycyclic (such as naphthyl) and can beunsubstituted or substituted. Preferred aryl groups include phenyl,naphthyl, furyl, thienyl, pyridyl, indolyl, quinolinyl or isoquinolinyl.

“Heterocyclic radical” refers to a stable, saturated, partiallyunsaturated, or aromatic ring, preferably containing 5 to 10, morepreferably 5 or 6, atoms. The ring can be substituted 1 or more times(preferably 1, 2, 3, 4 or 5 times) with substituent(s). The ring can bemono-, bi- or polycyclic. The heterocyclic group consists of carbonatoms and 1 to 3 heteroatoms independently selected from the groupconsisting of nitrogen, oxygen, and sulfur. The heteroatoms can beprotected or unprotected. Examples of useful heterocyclic groups includesubstituted or unsubstituted acridine, benzathiazoline, benzimidazole,benzofuran, benzothiophene, benzthiazole, benzothiophenyl, carbazole,cinnoline, furan, imidazole, 1H-indazole, indole, isoindole,isoquinoline, isothiazole, morpholine, oxazole, phenazine,phenothiazine, phenoxazine, phthalazine, piperazine, pteridine, purine,pyrazine, pyrazole, pyridazine, pyridine, pyrimidine, pyrrole,quinazoline, quinoline, quinoxaline, thiazole, 1,3,4-thiadiazole,thiophene, 1,3,5-triazines, and triazole.

“Substituted” means that the moiety contains at least one, preferably1-3 substituent(s). Suitable substituents include hydrogen (H) andhydroxyl (—OH), amino (—NH2), oxy (—O—), carbonyl (—CO—), thiol, alkyl,alkenyl, alkynyl, alkoxy, halo, nitrile, nitro, aryl, and heterocyclicgroups.

Photostability is measured using the following photostability test,which was adapted from photochemical activity tests well known in thetitania pigment and paint industry modified so that uncoated and coated(hydrophobic) powders could be evaluated in a single matrix. See“Titanium Dioxide Pigments: Correlation between Photochemical Reactivityand Chalking” from the National Lead Company 1949 (Industrial andEngineering Chemistry Volume 41 Number 3). The photooxidizable matrixused in the present photostability test is a 3:1 mixture (by weight) ofwhite petrolatum (White Petrolatum USP 100%) and glycerol (Glycerine USP96% Dow Chemical). The petrolatum and glycerol are first mixed until ahomogeneous matrix mixture is obtained. This matrix mixture is thenthoroughly blended with one part (by weight) of the powder to be tested,to form the test mixture. The final ratio is 3 parts white petrolatum: 1part glycerol: 1 part powder by weight. In the case of dispersions ofpowders the procedure is modified by using 1 part (by weight) of a 50 wt% powder dispersion in ethylhexyl benzoate (Finsolv® EB, Innospec, CASNumber 5444-75-7) blended with 0.5 parts glycerine and 3.5 parts whitepetrolatum to form the test mixture (so that the ratio ofpowder:glycerol by weight is 1:1). The test mixtures are then placed ina 1 inch diameter ×2 mm deep stainless steel well and sealed from theatmosphere with a 2 mm quartz cover. The test mixtures are then exposedto UV light in a Q-Labs QUV weatherometer using UVB bulbs at 0.35Wm⁻²s⁻¹ at a constant temperature of 50° C. Samples are exposed in theweatherometer for set times of 5 minutes, 10 minutes, 15 minutes and/or30 minutes; if no time is specified then only a 15 minute exposure isused. Color measurements are then made on each test mixture bycolorimetry on the exposed face through the quartz cover. Thecolorimeter used in the present studies was a Data Color-InternationalSpectraflash SF3000 Colorimeter, although equivalent instruments may beemployed. Photostability may be expressed as the total color change (ΔEin LAB* color space) for a stated UV exposure time. Both the zero timeabsolute color of each test mixture and a standard factory white tileare used as standards. A powder is not considered to be photostable inapplication if the photostability test results in the appearance of ablue color with an accompanying ΔE value greater than 8 after 15 minutesof UV exposure time.

For compositions other than TiO₂ where no direct color changenecessarily results from a lack of photostability, the test describedpreviously may be modified to include a suitable indicator dye. Suitableindicator dyes are those that can be dissolved in at least one of thecomponents of the carrier matrix, display inherent photostability in theabsence of radical generating species, and can be photo-bleached viareaction with radicals generated as a result of photo-excitation of theinorganic species to be tested. Azo dyes are typically well suited forthis test with the preferred dye being Disodium6-hydroxy-5-[(4-sulfophenyl)azo]-2-naphthalenesulfononate (SunsetYellow, Orange Yellow S; FD&C Yellow 6; C.I. 15985; E110; CAS Number2783-94-0). Photostability following UV exposure is indicated by thepersistence of the orange color due to the absorption band of the dye at480 nm. As in the test previously described, color is monitored viacolorimetry. In addition to the azo dyes, the dye DPPH(di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium,2,2-diphenyl-1-picrylhydrazyl; 1,1-diphenyl-2-picrylhydrazyl radical;2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl; diphenylpicrylhydrazyl;CAS Number 1898-66-4) can also be used in this test at the same loadinglevel. In this case, photostability following UV exposure is indicatedby the persistence of the purple color due to the absorption band of thedye at 520 nm.

Chemical reactivity is measured using the following chemical reactivitytest. A 20 dram glass vial is filled with 4.5 g of a stock solution of5% n-propyl gallate (propyl 3,4,5-trihydroxybenzoate, Aldrich) inisopropyl alcohol. One half of a gram of the powder to be evaluated isadded to the glass vial. The glass vial is then agitated, such as bybeing placed in a bath sonicator for 30 seconds. The mixture is allowedto stand for 30 minutes. The sample is then gently mixed using a pipetteand transferred to a cuvette (polycarbonate, polystyrene, or glass)having a path length of 1 cm. The total color change (ΔE) is thenmeasured against a factory white color standard using a DataColor-International Spectraflash SF3000 Colorimeter. Chemical reactivityis expressed as the total color change (ΔE). A powder is considered tobe chemically reactive in application if the chemical reactivity testresults in the appearance of a tan color with an accompanying ΔE valuegreater than 20.

Hydrophobicity is measured using the following hydrophobicity test (thistest is a visible water floatation test commonly used in the cosmeticsindustry, and is described in U.S. Pat. No. 4,454,288). Approximately 30mL of deionized water is placed into a glass jar. Approximately 3.0g±0.30 g of the powder to be tested is added into the glass jar. Theglass jar is tightly sealed, and the sample is swirled around 4 to 5times and vigorously shaken 4 to 5 times, so that intimate contactbetween the water and the powder is achieved. The powder is consideredto be hydrophobic if the powder is buoyant (floating on the surface ofthe water) and water is clear after 15 minutes. The sample is marginallyhydrophobic if the powder is not buoyant but the water is clear after 15minutes, or if the powder is buoyant but the water is not clear after 15minutes.

The fluidity of dispersions of powders is measured using the followingrun-off distance test. Dispersions are produced at 50% solids inethylhexyl benzoate (Finsolv® EB, Innospec). Three drops (75 mg) of thedispersion from a pipette are placed onto a clean glass plate substratewhile the surface is in a horizontal position. The glass substrate isthen held upright for 120 seconds at an angle of 90 degrees to allow thedispersion to flow. The fluidity of the dispersion is expressed as thedistance the dispersion flows from the origin. (This test was only usedduring initial screening; a measured run-off distance of 164±10 mm(reported as standard error) from the origin corresponds to a viscosityof 145±25 cP (reported as standard error) at a shear rate of 20 s⁻¹.). Acoated powder is considered to produce a pourable dispersion if at 50%solids in an ethylhexyl benzoate dispersion it shows a run-off distanceexceeding 100 mm.

The viscosity of dispersions of powders is measured using the followingviscosity test. Dispersions of the powders are prepared incapric/caprylic triglycerides (ALDO® MCT Special KFG, Lonza, CAS Number73398-61-5), ethylhexyl benzoate (Finsolv® EB, Innospec), and linearalkyl benzoate (Finsolv® TN C₁₂₋₁₅ Alkyl Benzoate CAS No.: 68411-27-8)at 50 wt % solids, unless otherwise specified. Viscosity is measured foreach dispersion using a Brookfield DVIII+ Ultra Rheometer with a CP52spindle at 25° C. Measurements are made at shear rates ranging from 0.1s⁻¹ to 100 s⁻¹.

DETAILED DESCRIPTION

Coated powders of TiO₂ and other selected metal oxides would bedesirable for use in UV protective topical skin compositions, and otherUV protective coatings. However, in order to be commercially desirable,such coated powders need to be (a) photostable, so that they do notsignificantly change color during exposure to UV light; (b) notchemically reactive, so that they do not react with or discolorcompositions during storage; and (c) may be formed into high weightloading dispersions which allow for high SPF values with minimalintroduction of carrier fluid and for cost efficient transport andstorage, but which have a viscosity low enough for easy handling andmixing when preparing consumer compositions. Dispersions of T-Cote 031,have a manageable viscosity at high weight loading, but have undesirablephotostability and chemical reactivity. Aeroxide T805 is photostable andnot chemically reactive, but high weight loading dispersions of thiscoated powder are too viscous for easy handling and mixing.

In an effort to develop a polymer coating which would provide both thephotostability and low chemical reactivity observed with powders coatedwith trifunctional alkoxy octylsilane (such as Aeroxide T805), and thelow viscosity high weight loading dispersions observed with powderscoated with poly(dimethylsiloxane) (such as T-Cote 031), combinations ofthese two surface treatments were used to prepare coated powders ofTiO₂. As expected, increasing the proportion of trifunctional alkoxyoctylsilane used to prepare the coating increased the photostability anddecreased the chemical reactivity; likewise, increasing the proportionof poly(dimethylsiloxane) used to prepare the coating reduced theviscosity of high weight loading dispersions. However, it was notpossible to increase the photostability and reduce the chemicalreactivity, and at the same time achieve a sufficiently low viscosity ofhigh weight loading dispersions. Therefore, a new approach was needed toachieve a coated powder having commercially desirable photostability andchemical reactivity, as well as a high weight loading dispersion withlow viscosity.

The photostability of Aeroxide T805 is thought to result from theformation of inorganic caps (such as SiO₃ moieties) on the particlesurface by reaction of the alkoxy groups of the trialkoxy alkylsilane.Therefore, substitution of the trifunctional alkoxy octylsilane withtetraethoxy silane would be expected to improve the photostability anddecrease chemical reactivity because of the possibility of an increasein inorganic cap formation on the particle surface as well as anincreased self-polymerization of the tetraethoxy silane and resultingincreased thickness of the inorganic caps at the particle surface. Thiscombination yielded a powder which displayed good photostability andchemical reactivity, but surprisingly, the dispersions were too viscous.Again, a new approach was need to achieve a coated powder havingcommercially desirable photostability and chemical reactivity, as wellas a high weight loading dispersion with low viscosity.

The present invention makes use of the discovery of coated powders whichare hydrophobic and photostable. The powder particles are nanoparticlescoated with a polymer, prepared by polymerizing a composition containingthe nanoparticles and at least three components: (A) a first alkoxysilane selected from the group consisting of a tetra-alkoxy silane, apoly(tetra-alkoxy silane), and mixtures thereof, (B) an organoalkoxysilane selected from the group consisting of mono-organoalkoxysilane, bi-organo alkoxysilane, tri-organo alkoxysilane, andmixtures thereof, and (C) a second alkoxy silane selected from the groupconsisting of a poly(dialkyl)siloxane, and mixtures thereof. The coatingformed contains moieties corresponding with each of the threecomponents: (A) silica moieties, (B) organo oxysilane moieties selectedfrom the group consisting of mono-organo oxysilane moieties, bi-organooxysilane moieties and tri-organo oxysilane moieties, and (C)poly(dialkyl)siloxane moieties. The coated nanoparticles can be used toform dispersions in cosmetically acceptable fluids which have highsolids and low viscosity. The dispersion may be used to prepare cosmeticcompositions for application to the skin, such as composition forprotecting skin from UV radiation (for example, sunscreens). Materialsconsidered to be cosmetically acceptable are those which are INCI(International Nomenclature of Cosmetic Ingredients) listed. Examples ofcosmetically acceptable fluids are ethylhexyl benzoate (EB), linearalkyl benzoate (LAB), caprylic/capric triglyceride (CTG), naturalproduct oils, and a variety of silicone fluids. Natural product oils areoils derived from seeds, beans, fruits, flowers, peels, leaves, and thelike, including their derivatives. Examples of natural product oils areolive oil and soybean oil.

The nanoparticles preferably comprise a metal oxide, for example zincoxide, titanium oxide, silicon oxide, aluminum oxide, iron oxide,bismuth oxide, cerium oxide, rare-earth oxides, infrared light absorbingbinary and ternary mixed metal oxides and mixtures thereof. Examplesinclude ZnO, TiO₂, SiO₂, Al₂O₃, Fe₂O₃, CeO₂, zirconium-cerium oxides,mixed zirconium-rare earth oxides containing cerium, aluminosilicates(including amorphous aluminosilicate, crystalline aluminosilicates, andpumice) and other silicates, aluminum oxides include alumina,aluminosilicates, magnesium aluminum oxides (for example, spinel), zincoxide doped with trivalent metal cations (including aluminum-doped ZnO),antimony-tin oxide (ATO), indium-tin oxide (ITO) and doped tungstenoxides. Metals, other ceramic compositions including carbides andnitrides and mixtures thereof, as well as mixtures with oxides, may alsobe used.

The nanoparticles have a particle size of at most 999 nm, including aparticle size of at most 100, 200, and 500 nm, more preferably aparticle size of 10 nm to 500 nm, most preferably a particle size of 15nm to 250 nm, such as 20, 30, 40, 50, 60, 70, 80, 90, and 100 nm.Preferably, the nanoparticles have an average particle size of at most999 nm, including an average particle size of at most 100, 200, and 500nm, more preferably an average particle size of 10 nm to 500 nm, mostpreferably an average particle size of 15 nm to 250 nm, such as 20, 30,40, 50, 60, 70, 80, 90, and 100 nm.

The nanoparticles may be coated by polymerizing the composition,preferably without solvents and with at least some of the composition inthe gas phase. The composition includes (A) a first alkoxy silaneselected from the group consisting of a tetra-alkoxy silane, apoly(tetra-alkoxy silane), and mixtures thereof, (B) an organoalkoxysilane selected from the group consisting of mono-organoalkoxysilane, bi-organo alkoxysilane, tri-organo alkoxysilane, andmixtures thereof, and (C) a second alkoxy silane selected from the groupconsisting of a poly(dialkyl)siloxane, and mixtures thereof. Preferably,the first alkoxy silane is present in an amount of 0.5 to 10% by weightof the nanoparticles, more preferably 2 to 8% by weight of thenanoparticles, and most preferably 3 to 5% by weight of thenanoparticles, including 3.5, 4, and 4.5%. Preferably, the organoalkoxysilane is present in an amount of 0.5 to 10% by weight of thenanoparticles, more preferably 1 to 6% by weight of the nanoparticles,and most preferably 1.5 to 4% by weight of the nanoparticles, including2, 2.5, 3, and 3.5%. Preferably, the second alkoxy silane is present inan amount of 1 to 22% by weight of the nanoparticles, more preferably 3to 18% by weight of the nanoparticles, and most preferably 7 to 15% byweight of the nanoparticles, including 7.5, 8, 8.5, 9, 9.5, 10, 10.5,11, 11.5, 12, 12.5, 13, 13.5, 14, and 14.5%.

The first alkoxy silane may be a tetra-alkoxy silane, apoly(tetra-alkoxy silane), or mixtures thereof. Tetra-alkoxy silanes arecompounds of the formula (R^(a)O)₄Si, where each R^(a) is an organicgroup which may be the same or different, and each R^(a) is preferablyan alkyl groups having 1 to 20 carbon atoms, more preferably 1 to 10carbon atoms, including 2, 3, 4, 5, 6, 7, 8, and 9 carbon atoms,including methyl, ethyl, and propyl. An example is tetraethoxy silane(TEOS). A poly(tetra-alkoxy silane) is an oligomer of one or moretetra-alkoxy silanes, formed by partial hydrolysis. Preferably thepoly(tetra-alkoxy silane) contains 2 to 14 monomer units, morepreferably 4 to 10 monomer units, including 5, 6, 7, 8, and 9.

The organo alkoxysilane is selected from the group consisting ofmono-organo alkoxysilane, bi-organo alkoxysilane, tri-organoalkoxysilane, and mixtures thereof. The organo alkoxysilane arecompounds of the formula R¹ _(n)Si(OR^(b))_(4−n) where n is 1, 2 or 3.R¹ is an organic group, such as alkyl (for example, linear alkyl,branched alkyl, cyclic alkyl, glycidoxyalkyl, methancryloxyalkyl andaminoalkyl), aryl, vinyl and heteroaryl. Examples of R¹ include methyl,ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl,dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, andoctadecyl. Preferably, R¹ contains 1 to 20 carbon atoms, more preferably1 to 10 carbon atoms, including 2, 3, 4, 5, 6, 7, 8 and 9 carbon atoms.Each R^(b) is an organic group which may be the same or different, andeach R^(b) is preferably an alkyl groups having 1 to 20 carbon atoms,more preferably 1 to 10 carbon atoms, including 2, 3, 4, 5, 6, 7, 8 and9 carbon atoms, including methyl, ethyl, and propyl. An example of anorgano alkoxysilane is triethoxy octylsilane.

The second alkoxy silane is selected from the group consisting of apoly(dialkyl)siloxane, and mixtures thereof. Poly(dialkyl)siloxanes arepreferably oligomers of the formula R^(c)O(SiR² ₂)(R² ₂SiO)_(n)(SiR²₂)OR^(c), where n is an integer of 2 to 14, preferably 4 to 10,including 5, 6, 7, 8 and 9. Each R² is an organic group such as methyl,ethyl, or phenyl, and each R^(c) is an end blocking group such as alkylincluding methyl, ethyl, and propyl to form an alkyloxy group, or H toform a hydroxyl group; hydroxy and alkyloxy groups are both reactivegroups. It is also possible that 1 to 3 of the R² groups are hydroxyland/or alkyloxy groups. R² and R^(c) each independently preferablycontain 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms,including 2, 3, 4, 5, 6, 7, 8 and 9 carbon atoms. Preferably, thepoly(dialkyl)siloxane is a polydimethylsiloxane or apolydiethylsiloxane. Preferably, the poly(dialkyl)siloxanes have aweight average molecular weight of 200 to 1400, more preferably 400 to700.

Typically, the nanoparticles and the three components of the compositionare thoroughly mixed together, and then placed into a sealed vessel. Thevessel is then evacuated and heated to a temperature where at least twoof components form vapor. The temperature is maintained for sufficienttime to allow polymerization and formation of a coating on thenanoparticles, preferably with continuous mixing during thepolymerization process. The vessel is then flooded with an inert gasstream which allows the removal of volatile by-products such as alcoholsand is subsequently allowed to cool to room temperature. The polymercoating formed contains moieties of each of the three silanes: (1)silica moieties, (2) organo oxysilane moieties selected from the groupconsisting of mono-organo oxysilane moieties, bi-organo oxysilanemoieties and tri-organo oxysilane moieties, and (3)poly(dialkyl)siloxane moieties.

Preferably, the temperature of polymerization is 80° C. to 120° C., morepreferably 90° C. to 110° C., including 92, 94, 96, 98, 100, 102, 104,106, and 108° C. Preferably the amount of time for polymerization is 0.5to 10 hours, more preferably 1 to 6 hours, including 2, 3, 4, and 5hours.

Silica moieties are Si(O)₄ groups which bond to 4 atoms, and may also bepresent in clusters such as [OSi(O₂)]_(n)O, where n is 2 to 14, morepreferably 4 to 10, including 5, 6, 7, 8 and 9. Organo oxysilanemoieties are R¹ _(n)Si(O)_(4−n) groups which bond to “4-n” other atoms,with n an integer of 1, 2 or 3. R¹ is an organic group, such as alkyl(for example, linear alkyl, branched alkyl, cyclic alkyl,glycidoxyalkyl, methancryloxyalkyl and aminoalkyl), aryl, vinyl andheteroaryl. Examples of R¹ include methyl, ethyl, propyl, butyl, pentyl,hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tridecyl, tetradecyl,pentadecyl, hexadecyl, heptadecyl, and octadecyl. Preferably, R¹contains 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms,including 2, 3, 4, 5, 6, 7, 8 and 9 carbon atoms. An example of anorgano oxysilane moiety is octylsilane.

Poly(dialkyl)siloxane moieties are O(SiR² ₂)(R² ₂SiO)_(n)(SiR² ₂)O orO(SiR² ₂)(R² ₂SiO)_(n)(SiR² ₂)OR^(c) groups which bond to other atoms,where n is an integer of 2 to 14, preferably 4 to 10, including 5, 6, 7,8, and 9. Each R² is independently an organic group such as methyl,ethyl, or phenyl, and each R^(c) is an end blocking groups such as alkylincluding methyl, ethyl, and propyl to form an alkyloxy group, or H toform a hydroxyl group; hydroxy and alkyloxy groups are both reactivegroups. It is also possible that 1 to 3 of the R² groups are hydroxyland/or alkyloxy groups. R² and R^(c) each independently preferablycontain 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms,including 2, 3, 4, 5, 6, 7, 8, and 9 carbon atoms. Preferably, thepoly(dialkyl)siloxane moiety is a polydimethylsiloxane moiety or apolydiethylsiloxane moiety.

A variety of techniques are available to analyze the coated powder ofthe present invention. The inorganic oxide particles may be dissolvedwith various acids, determining the relative amount of polymer andinorganic oxide, and then the remaining polymer coating may be examinedusing FTIR (Fourier Transform Infrared Spectroscopy) to determine thepresence of different moieties and the relative amounts of each moiety.Other techniques, such as mass spectrometry, TGA (ThermogravimetricAnalysis), or ICP (Inductively Coupled Plasma Spectroscopy) may also beused to establish relative monomer unit ratios. A baseline may beestablished by using a standard of known composition.

The coated powder may also be analyzed by solid state NMR, examining ¹³Cand ²⁹Si NMR signals to determine the presence of different moieties andthe relative amounts of each moiety. Furthermore, the inorganic oxideparticles may be dissolved with various acids, and the remaining polymercoating may be analyzed by NMR, examining ¹³C and ²⁹Si NMR signals todetermine the presence of different moieties and the relative amounts ofeach moiety. A baseline may be established by using a standard of knowncomposition.

The coated powders may be examined for properties using thephotostability test, the chemical reactivity test and the hydrophobicitytest. Preferably, the coated powders have a photostability of ΔE=0 to 7,more preferably ΔE=0 to 5, most preferably ΔE=0, 1, 2, 3 or 4.Preferably, the coated powders have a chemical reactivity of ΔE=0 to 20,more preferably ΔE=0 to 17, most preferably ΔE=0, 1, 2, 3, 4, 5, 6, 7,8, 9, 10, 11, 12, 13, 14, 15, or 16. Preferably the coated powders arehydrophobic or marginally hydrophobic, most preferably hydrophobic.

The coated powder may be used to form dispersions with non-polarliquids, preferably cosmetic oils, such as capric/caprylictriglycerides, linear alkyl benzoate, ethylhexyl benzoate, naturalproduct oils, and silicone oils. Preferably, the dispersions contain atleast 40% by weight coated powder (solids), more preferably at least 50%by weight coated powder (solids), including at least 55% by weightcoated powder (solids), at least 60% by weight coated powder (solids),and at least 65% by weight coated powder (solids), such as 50-65% byweight coated powder (solids), and 55-60% by weight coated powder(solids). Such dispersions may be made by a variety of conventionalmixing processes, including mixing with a rotor-stator machine,planetary mixing, high-pressure homogenizers, ultra-sonic mixing, andmedia milling. An adjunct emulsifier or dispersant may be included inthe dispersions. Examples include triceteareth-4 phosphate (Hostaphat KW340 D; Clariant) at 5-15% by weight of solids.

Surprisingly, high solids dispersions of the coated powders haverelatively low viscosity. Preferably, the viscosity is at most 60,000cP, more preferably at most 30,000 cP, most preferably at most 6,000 cP.Examples include a viscosity of 1,000 to 50,000 cP, and 5,000 to 30,000cP.

The coated powder, as well as the dispersions of the coated powder maybe used in a variety of products. They may be added to dermatologicalcompositions to provide UV protection to skin, especially in the case ofTiO₂ and ZnO containing coated powders; the coated powder may also beadded to such compositions as inorganic pigments. The coated powders mayalso be added to shampoos, lotions, gels, hairsprays, aerosol foamcreams or emulsions, for washing, coloring and for styling hair, whilealso providing UV protection to hair. They may be added to paints,sealants and other coatings for wood, plastics and other constructionmaterials; again, UV protection is provided in the case of TiO₂ and ZnOcontaining coated powders. They may also be added to resins, filledpolymers and plastics, and inks. Magnetic fluids may be prepared whenthe metal oxide is magnetic, as in the case of certain iron oxides andrare-earth oxides.

Cosmetic and dermatological preparations may include cosmeticingredients, auxiliaries and/or additives, for example, co-emulsifiers,fats and waxes, stabilizers, thickeners, biogenic active ingredients,film formers, fragrances, dyes, pearlizing agents, preservatives,pigments, electrolytes, and pH regulators. Suitable co-emulsifiers are,preferably, known W/O and also O/W emulsifiers, for example,polyglycerol esters, sorbitan esters or partially esterified glycerides.Typical examples of fats are glycerides; waxes such as beeswax, paraffinwax or microcrystalline waxes, optionally in combination withhydrophilic waxes. Stabilizers including metal salts of fatty acids, forexample, magnesium, aluminum and/or zinc stearate. Examples ofthickeners include crosslinked polyacrylic acids and derivativesthereof, polysaccharides, such as xanthan gum, guar gum, agar, alginatesand tyloses, carboxymethylcellulose and hydroxyethylcellulose, and fattyalcohols, monoglycerides and fatty acids, polyacrylates, polyvinylalcohol and polyvinylpyrrolidone. Biogenic active ingredients includeplant extracts, protein hydrolyzates and vitamin complexes. Customaryfilm formers include, for example, hydrocolloids, such as chitosan,microcrystalline chitosan or quaternary chitosan, polyvinylpyrrolidone,vinylpyrrolidone/vinyl acetate copolymers, polymers of the acrylic acidseries, and quaternary cellulose derivatives. Examples of preservativesinclude parabens, diazolidinyl urea, iodopropynyl butylcarbamate, andsorbic acid. Examples of pearlizing agents include glycol distearicesters, such as ethylene glycol distearate, fatty acids and fatty acidmonoglycol esters. Dyes which may be used are the substances suitableand approved for cosmetic purposes. Antioxidants, such as amino acids,retinol, flavonoids, polyphenols, vitamin C and tocopherols, may also beincluded.

The cosmetic and dermatological preparations may be in the form of asolution, dispersion or emulsions; for example sunscreen preparationsmay be in liquid, paste or solid form, for example as water-in-oilcreams, oil-in-water creams and lotions, aerosol foam creams, gels,oils, marking pencils, powders, sprays or alcohol-aqueous lotions.Solvents for these compositions include water; oils, such astriglycerides of capric acid or of caprylic acid, as well as castor oil;fats, waxes and other natural and synthetic fatty substances, esters offatty acids with alcohols of low carbon number, for example withisopropanol, propylene glycol or glycerol, or esters of fatty alcoholswith alkanoic acids of low carbon number or with fatty acids; alcohols,diols or polyols of low carbon number, and ethers thereof, preferablyethanol, isopropanol, propylene glycol, glycerol, ethylene glycol,ethylene glycol monoethyl or monobutyl ether, propylene glycolmonomethyl, monoethyl or monobutyl ether, diethylene glycol monomethylor monoethyl ether. Other examples include isopropyl myristate,isopropyl palmitate, isopropyl stearate, isopropyl oleate, n-butylstearate, diisopropyl adipate, n-hexyl laurate, n-decyl oleate, glycerylstearate, isooctyl stearate, isononyl stearate, isononyl isononanoate,2-ethylhexyl palmitate, 2-ethylhexyl laurate, 2-hexyldecyl stearate,2-octyldodecyl palmitate, oleyl oleate, oleyl erucate, erucyl oleate,and erucyl erucate.

The cosmetic and dermatological preparations may be in the form of solidsticks, and may include natural or synthetic waxes, fatty alcohols orfatty acid esters, liquid oils for example paraffin oils, castor oil,isopropyl myristate, semisolid constituents for example petroleum jelly,lanolin, solid constituents such as beeswax, ceresine andmicrocrystalline waxes and ozocerite, and high-melting waxes includingcarnauba wax and candelilla wax.

Cosmetic preparations may be in the form of gels and preferably includewater, organic thickeners, for example gum arabic, xanthan gum, sodiumalginate, cellulose derivatives such as methylcellulose,hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose,hydroxpropylmethylcellulose and inorganic thickeners, such as aluminumsilicates, for example, bentonites, or a mixture of polyethylene glycoland polyethylene glycol stearate or distearate.

The coated powders and dispersions may also be included in paints,sealants and other coatings, which may also contain binders such aspolyacrylates, polyurethanes, polyalkyds, polyepoxides, polysiloxanes,polyacrylonitriles and/or polyesters. Organic solvents may also bepresent, including ethanol, butyl acetate, ethyl acetate, acetone,butanol, alkanes, methanol, propanol, and pentanol; ethers/acetals suchas tetrahydrofuran and 1,4-dioxane; ketones such as diacetone alcohol,and methyl ethyl ketone; and polyhydric alcohol derivatives such asethylene glycol, propylene glycol, and diethylene glycol or mixturesthereof. These compositions may be used to coat a variety of substrates,including wood, PVC (polyvinyl chloride), plastic, steel, aluminum,zinc, copper, MDF (medium density fiberboard), glass and concrete.Depending on which coated powders are included, the compositions providethe substrate with a coating that may be transparent, UV-resistant,and/or provide greater scratch resistance.

The coated powder and dispersions may be blended with a resin, toprovide an organic polymer composite. Examples of resins include,polyethylene, polypropylene, polystyrene, polyethylene terephthalate, AS(acrylonitrile styrene) resins, ABS (acrylonitrile butadiene styrene)resins, AES (acrylonitrile ethylene styrene) resins, polyvinylidenechloride, methacrylic resins, polyvinyl chloride, polyamides,polycarbonates, polyallyl esters, polyimides, polyacetals, polyetherketones, polyether sulfones, polyphenyl oxides and polyphenylenesulfides, as well as mixtures thereof. Also present in thesecompositions may be coloring agents, fluorescent agents, and additives,such as antioxidants, anti-aging agents, UV-absorbers, lubricants,antistatic agents, surfactants, fillers (the coated powder anddispersions may also act as fillers), plasticizers, stabilizers, blowingagents, expanding agents, electroconductive powder, electroconductiveshort fiber, deodorizing agents, softening agents, thickeners,viscosity-reducing agents, diluents, water-repellent agents,oil-repellent agents, cross-linking agents and curing agents. Theseorganic polymer compositions may be shaped by a variety of techniques,including injection molding, blow molding, extrusion molding, calendermolding, flow molding, compression molding, melt-blown molding, and thespun bond method, whereby shape-imparted products such as fiber, thread,film, sheets, tapes, and injection-molded products and shaped bodiessuch as hollow thread, pipes, and bottles may be produced.Alternatively, the compositions can be subjected to secondary moldingmethods generally applied to thermoplastic resins such as vacuumforming, air pressure forming, and laminate molding.

EXAMPLES Example 1

This Example illustrates a coated nanocrystalline TiO₂ powder of thepresent invention. A 10.0 g charge of nanocrystalline TiO₂ (specificsurface area=45 m²/g, corresponding average particle size=32 nm, P25S;Evonik) is loaded into a laboratory blender together with a mixture oftetraethoxy silane (0.4 g), triethoxy octylsilane (0.3 g) and hydroxyterminated polydimethylsiloxane (0.95 g). The mixture is homogenized for30 seconds and then transferred to a glass container which issubsequently sealed. The sealed container is then transferred to an ovenwhere it is heated to a temperature of 90° C. and held for 4 hours. Theresultant coated powder is then dried by unsealing the container andreturning the container to the same oven where it is held at atemperature of 100-110° C. and held for 1.5 hours. The resultant coatedpowder is highly hydrophobic, passes the n-propyl gallate test(ΔE=16.74) and passes the photostability test (ΔE=3.65). A 50% solidsdispersion in ethylhexyl benzoate is highly pourable and fluid showing arun-off distance of 128 mm.

Example 2

This Comparative Example illustrates a coated nanocrystalline TiO₂powder outside the scope of the present invention. A 10.0 g charge ofnanocrystalline TiO₂ (specific surface area=45 m²/g, correspondingaverage particle size=32 nm, P25S; Evonik) is loaded into a laboratoryblender together with a mixture of tetraethoxy silane (0.4 g) andhydroxy terminated polydimethylsiloxane (1.2 g). The mixture ishomogenized for 30 seconds and then transferred to a glass containerwhich is subsequently sealed. The sealed container is then transferredto an oven where it is heated to a temperature of 100° C. and held for 2hours. The resultant coated powder is then dried by unsealing thecontainer and returning the container to the same oven where it is heldat a temperature of 100-110° C. and held for 1.5 hours. The resultantcoated powder is hydrophobic, fails the n-propyl gallate test(ΔE=24.18), and passes the photostability test (ΔE=5.92). A 50% solidsdispersion in ethylhexyl benzoate displays poor fluidity showing arun-off distance of 84 mm. The dispersion behavior and chemicalreactivity of this coated powder render it unsuitable for commercialuse.

Example 3

This Comparative Example illustrates a coated nanocrystalline TiO₂powder outside the scope of the present invention. A 10.0 g charge ofnanocrystalline TiO₂ (specific surface area=45 m²/g, correspondingaverage particle size=32 nm, P25S; Evonik) is loaded into a laboratoryblender together with a mixture of triethoxy octylsilane (0.4 g) andhydroxy terminated polydimethylsiloxane (1.6 g). The mixture ishomogenized for 30 seconds and then transferred to a glass containerwhich is subsequently sealed. The sealed container is then transferredto an oven where it is heated to a temperature of 100° C. and held for 2hours. The resultant coated powder is then dried by unsealing thecontainer and returning the container to the same oven where it is heldat a temperature of 100-110° C. and held for 1.5 hours. The resultantcoated powder is hydrophobic, and displays good fluidity at 50% solidsin ethylhexyl benzoate but fails the photostability test (ΔE=11.47),making it unsuitable for commercial use.

Example 4

This Comparative Example illustrates a coated nanocrystalline TiO₂powder outside the scope of the present invention. A 10.0 g charge ofnanocrystalline TiO₂ (specific surface area=45 m²/g, correspondingaverage particle size=32 nm, P25S; Evonik) is loaded into a laboratoryblender together with a mixture of tetraethoxy silane (0.2 g) and),triethoxy octylsilane (0.8 g). The mixture is homogenized for 30 secondsand then transferred to a glass container which is subsequently sealed.The sealed container is then transferred to an oven where it is heatedto a temperature of 100° C. and held for 2 hours. The resultant coatedpowder is then dried by unsealing the container and returning thecontainer to the same oven where it is held at a temperature of 100-110°C. and held for 1.5 hours. The resultant coated powder is hydrophobic,but displays poor fluidity and forms a paste at only 40% solids inethylhexyl benzoate making it unsuitable for commercial use.

Example 5

This Comparative Example illustrates the properties of commerciallyavailable TiO₂ nanopowders that are outside the scope of the presentinvention.

Aeroxide Aeroxide T-Cote 031 T-805 031 P25S Test (Sensient) (Evonik)(Evonik) Coating Poly dialkyl Octyl silane None siloxane HydrophobicityFail Pass Fail Photostability (ΔE at 15 min) Fail Pass Fail 12.29 7.6915.44 Chemical Reactivity Fail Pass Fail (n-Propyl Gallate Test) 31.6420.17 37.42 Pourability Pass (Highly Fail (Thick Fail (Thick (50% Solidsin ethylhexyl Fluid) Paste) Paste) benzoate) 235 mm 2 mm 0 mm Run-offdistance

This Comparative Example illustrates that each of the commerciallyavailable TiO₂ nanopowders possesses at least one undesirable propertyfor use in commercial application.

Example 6

This Example illustrates a high solids dispersion of the presentinvention that is suitable for addition to cosmetic formulations. 460 gof Ethylhexyl benzoate (Finsolv® EB; Innospec) and 40 g of an emulsifierare added to a jacketed steel container which is maintained at aconstant temperature of 30° C. The emulsifier, triceteareth-4 phosphate(Hostaphat KW 340 D; Clariant) is a waxy solid, anionic O/W emulsifierdesigned to be used in formulations requiring some level of viscositysuch as cream preparations. The contents of the vessel are pre-mixedusing a Cowels saw-tooth high shear impeller under mild mixingconditions for 5 minutes until the mixture is homogeneous. In theconfiguration used in this example, the impeller blade diameter is ⅓ ofthe vessel diameter and is placed 1 blade diameter from the bottom ofthe vessel. 500g of the coated TiO₂ nanopowder of Example 1 is added tothe liquid contents under mild mixing until all the powder is wetted.The mixer speed is then increased to 2500 rpm for 15 minutes. Theresultant dispersion is pourable and has a viscosity of 4600 cP.

Example 7

This Example illustrates a coated nanocrystalline ZnO powder of thepresent invention. A 10 g charge of nanocrystalline ZnO (specificsurface area=17 m²/g, corresponding average particle size=63 nm) isloaded into a laboratory blender together with a 1.0 g mixture oftetraethoxy silane, triethoxy octylsilane and hydroxy terminatedpolydimethylsiloxane in the same relative proportions as in Example 1.The mixture is homogenized for 30 seconds and then transferred to aglass container which is subsequently sealed. The sealed container isthen transferred to an oven where it is heated to a temperature of100-110° C. and held for 1.5 hours. The resultant coated powder is thendried by unsealing the container and returning the container to the sameoven where it is held at a temperature of 100-110° C. and held for 1.5hours. The resultant coated powder is highly hydrophobic and passes thephotoactivity test using DPPH as the indicator dye. The coated powder ofthis Example can be dispersed at 65% solids in capric/caprylictriglycerides (ALDO® MCT Special KFG, Lonza, CAS Number 73398-61-5),ethylhexyl benzoate (Finsolv® EB, Innospec), and linear alkyl benzoate(Finsolv® TN C₁₂₋₁₅ Alkyl Benzoate CAS No.: 68411-27-8) to yieldpourable dispersions having viscosities below 10,000 cP. The coatedpowder of this example and corresponding dispersions are suitable foruse in cosmetic sunscreen formulations.

Example 8

This Example illustrates a coated nanocrystalline Fe₂O₃ powder of thepresent invention. A 10 g charge of nanocrystalline γ-Fe₂O₃ (specificsurface area=38 m²/g, corresponding average particle size=30 nm) isloaded into a laboratory blender together with a 1.5 g mixture oftetraethoxy silane, triethoxy octylsilane and hydroxy terminatedpolydimethylsiloxane in the same relative proportions as in Example 1.The mixture is homogenized for 30 seconds and then transferred to aglass container which is subsequently sealed. The sealed container isthen transferred to an oven where it is heated to a temperature of100-110° C. and held for 1.5 hours. The resultant coated powder is thendried by unsealing the container and returning the container to the sameoven where it is held at a temperature of 100-110° C. and held for 1.5hours. The resultant coated powder is highly hydrophobic. The coatedpowder of this example can be dispersed at 50% solids in ethylhexylbenzoate (Finsolv® EB, Innospec) to yield a pourable dispersion having aviscosity below 3,000 cP. The coated powder of this example is suitablefor use in cosmetic preparations, ferrofluids, and magneto-rheologicalfluids.

Example 9 Prophetic

This Example illustrates a water-in-oil emulsion cosmetic sunscreenpreparation of the present invention containing only inorganic UVscreening agents.

The following oil-phase ingredients are added to a heated vessel andmixed at low intensity at 80° C. until clear.

Ingredients Parts by Weight Emulsifier (Abil EM-90: Bis-PEG/PPGDimethicone, 5.0 Cyclopentasiloxane; Evonik-Goldschmidt GmbH)2-Ethylhexyl Palmitate (CAS# 29806-73-3, Crodamol 11.0 OP; Croda Ltd.)Decamethylcyclopentasiloxane (245 Silicone Oil; 7.5 Dow Corning) CetylDimethicone (Abil Wax 9801; Evonik- 3.0 Goldschmidt GmbH) White MineralOil (Carnation Oil; Sonneborn) 2.0 Emollient White Ceresine Wax(Ceresine Sp-252; 1.0 Strahl & Pitsch) Emollient (Castorwax MP70Hydrogenated Castor 0.5 Oil; Vertellus)

The oil-phase mixture is then cooled to 60° C. and mixed with the coatedTiO₂ powder of Example 1 (12.0 parts by weight) and subsequently passedthrough a media mill until the mixture is homogeneous. This mixture isthen cooled to 45° C.

The following water-phase ingredients are combined in a separate vessel.

Ingredients Parts by Weight Deionized water 56.5 Preservative (GermabenII; ISP) 1.0 Sodium Chloride 0.5

The milled oil-phase mixture and the water phase mixture are mixed untila homogeneous emulsion is formed. Note that optional fragrance (0.2parts by weight) may be substituted for the equivalent amount ofdeionized water.

Example 10 Prophetic

This Example illustrates a water-in-oil emulsion cosmetic sunscreenpreparation of the present invention containing a combination of organicand inorganic UV screening agents. This example shows that the highsolids dispersions of the present invention can be used to avoid timeconsuming milling operations typical in the manufacture of commercialtopical sunscreens containing inorganic UV screening agents.

The following oil-phase ingredients are added to a heated vessel andmixed at low intensity at 80° C. until homogeneous and subsequentlycooled to 45° C.

Ingredients Parts by Weight Emulsifier (Abil EM-90: Bis-PEG/PPGDimethicone, 5.0 Cyclopentasiloxane; Evonik-Goldschmidt GmbH) Ethylhexylbenzoate (Finsolv ® EB; Innospec) 4.0 50% Solids TiO₂ dispersion inEthylhexyl benzoate 12.0 (Finsolv ® EB; Innospec) of Example 1 65%Solids ZnO dispersion in Ethylhexyl benzoate 9.0 (Finsolv ® EB;Innospec) of Example 7 Decamethylcyclopentasiloxane (245 Silicone Oil;7.5 Dow Corning) Octylmethyl Cinnamate 5.0 Octocrylene 7.0 CetylDimethicone (Abil Wax 9801; Evonik- 3.0 Goldschmidt GmbH) White MineralOil (Carnation Oil; Sonneborn) 2.0 Emollient White Ceresine Wax(Ceresine Sp-252; 1.0 Strahl & Pitsch) Emollient (Castorwax MP70Hydrogenated Castor 0.5 Oil; Vertellus)

The following water-phase ingredients are combined in a separate vessel.

Ingredients Parts by Weight Deionized water 40.5 Propylene Glycol, USP2.0 Preservative (Germaben II; ISP) 1.0 Sodium Chloride 0.4 Sodium EDTA0.1

The oil-phase mixture and the water phase mixture are mixed until ahomogeneous emulsion is formed. Note that optional fragrance (0.2 partsby weight) may be substituted for the equivalent amount of deionizedwater.

Example 11 Prophetic

This Example illustrates a plastic composition of the present invention.The coated TiO₂ nanopowder of Example 1 (2.0% by weight) is mixed withlinear low density polyethylene (Petrothene NA940 Film Extrusion Grade;LDPE; Lyondell) (98% by weight) in a twin screw extruder at temperaturesranging from 165° C.-220° C., with 185° C. being typical. The resultantUV stabilized plastic is suitable for extrusion into a master-batch orinto films or finished articles. Adjunct components such as colorants,slip/antiblock agents, thermal stabilizers and the like can be added tothe composition as required by the specific application.

Example 12 Prophetic

This Example illustrates an example of a UV curable coating compositionof the present invention. The following ingredients are mixed untilhomogeneous.

Ingredients Parts by Weight Bisphenol A epoxy acrylate 80% in 44.0neopentylglycol propoxylatediacrylate Propoxylated neopentyl glycoldiacrylate 30.9 Ditrimethylolpropane tetraacrylate 3.2 Benzophenone 6.0Acrylated amine synergist (Chivacure OPD; 9.9 Campbell and Co.)Photoinitiator (Irgacure 184; BASF) 2.0 Rheology modifier (Bentone 27;Elementis 0.4 Specialties) Coated TiO₂ nanopowder of Example 1 3.6

The composition of this example can be applied as a wet film to asubstrate using a wire-wound rod or spray gun and subsequently curedusing UV radiation to yield a UV protective hardcoat.

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WO 2009/131910

WO 95/23192

What is claimed is:
 1. A coated powder comprising: (a) nanoparticles,and (b) a coating, on the surface of the nanoparticles, comprising (1)silica moieties, (2) organo oxysilane moieties selected from the groupconsisting of mono-organo oxysilane moieties, bi-organo oxysilanemoieties and tri-organo oxysilane moieties, and (3)poly(dialkyl)siloxane moieties, wherein the coated powder isphotostable, not chemically reactive, is hydrophobic, and is pourable,wherein pourable means that a dispersion comprising 50 wt % coatedpowder in ethylhexyl benzoate shows a run-off distance exceeding 100 mm.2. The coated powder of claim 1, wherein the nanoparticles comprise atleast one oxide selected from the group consisting of zinc oxides,titanium oxides, silicon oxides, aluminum oxides, iron oxides, bismuthoxides, tin oxides, indium oxides, tungsten oxides and rare-earth metaloxides.
 3. The coated powder of claim 2, wherein the nanoparticlescomprise at least one oxide selected from the group consisting of ZnO,TiO₂, SiO₂, Al₂O₃, Fe₂O₃, CeO₂ Bi₂O₃, antimony-tin oxide, indium-tinoxide, doped WO₃, and mixtures thereof.
 4. The coated powder of claim 1,wherein the nanoparticles have an average particle size of 10-500 nm. 5.The coated powder of claim 1, wherein the organo oxysilane moieties eachhave the formula R¹ _(n)SiO_(4−n), with n=1, 2 or 3, and each R¹ groupis independently selected from the group consisting of alkyl, alkenyl,alkynyl, aryl and heterocyclic radical.
 6. The coated powder of claim 5,wherein each R¹ group has 1-18 carbon atoms and is independentlyselected from the group consisting of alkyl, alkenyl and aryl.
 7. Thecoated powder of claim 6, wherein each R¹ group is independentlyselected from the group consisting of alkyl, aryl, vinyl,glycidoxyalkyl, methacryloxyalkyl, aminoalkyl and mercaptoalkyl.
 8. Thecoated powder of claim 1, wherein the poly(dialkyl) siloxane moietieseach have the formula O(SiR² ₂)(R² ₂SiO)_(n)(SiR² ₂)O or O(SiR² ₂)(R²₂SiO)_(n)(SiR² ₂)OR^(c), where n is an integer of 2 to 14, each R² groupis an alkyl, and R^(c) is selected from the group consisting of H,methyl, ethyl and propyl.
 9. The coated powder of claim 1, wherein thepoly(dialkyl) siloxane moieties are polydimethyl siloxane moieties orpolydiethyl siloxane moieties.
 10. The coated powder of claim 1, whereinthe organo oxysilane moieties are present in an amount of 1-5% of theweight of the nanoparticle.
 11. The coated powder of claim 1, whereinthe poly(dialkyl)siloxane moieties are present in an amount of 1-20% ofthe weight of the nanoparticle.
 12. A process for producing a coatedpowder, comprising coating nanoparticles with a polymer, by polymerizinga composition comprising (i) the nanoparticles, (ii) a first alkoxysilane selected from the group consisting of a tetra-alkoxy silane, apoly(tetra-alkoxy silane), and mixtures thereof, (iii) an organoalkoxysilane selected from the group consisting of mono-organoalkoxysilane, bi-organo alkoxysilane, tri-organo alkoxysilane, andmixtures thereof, and (iv) a second alkoxy silane selected from thegroup consisting of a poly(dialkyl)siloxane, and mixtures thereof,wherein the coated powder is photostable, not chemically reactive, ishydrophobic, and is pourable, wherein pourable means that a dispersioncomprising 50 wt % coated powder in ethylhexyl benzoate shows a run-offdistance exceeding 100 mm.
 13. A dispersion, comprising the coatedpowder of claim 1, and a liquid carrier.
 14. The dispersion of claim 13,comprising at least 50% by weight of the coated powder, wherein thedispersion shows a run-off distance exceeding 100 mm.
 15. The dispersionof claim 13, wherein the dispersion has a viscosity of at most 10,000 cPwhen measured at 25° C. at shear rates ranging from 0.1 sec⁻¹ to 100sec⁻¹.
 16. The dispersion of claim 13, wherein the liquid carrier isethylhexyl benzoate.
 17. A composition comprising the coated powder ofclaim 1, wherein the composition is a paint, stain, coating or ink. 18.A coated powder, prepared by the process of claim
 12. 19. A method ofprotecting skin from light, comprising coating skin with a compositioncomprising the coated powder of claim
 1. 20. A method of protecting skinfrom light, comprising coating skin with the dispersion of claim 13.